universal testing machine

[JohnCoker]

I have some tests I want to do on rocket construction, specifically comparing 3D printed parts to traditional techniques, for which I need a UTM.

However, I don't know enough about them yet. First question is what capacity do I need? I want to be able to do basic tests such as tension and 3-point bend on materials such as plywood and G10. I also want to be able to do compression tests with a piston on assemblies such as a MMT inside a body tube and pull tests such as ripping fins off.

Second question is how can I get one for a not-crazy price? I got a quote for a 30KN machine from Instron and as you might expect, that's too expensive. I don't care about formal calibration (as long as the numbers are close to accurate and consistent). I looked on AliExpress and they have machines for about a tenth of the price, but I'm guessing they're not complete (load cells, fixtures, computer, software, etc.).

Volume is probably where I'm most flexible. I think 500mm should be enough for compress and pull tests where I don't need to use the jaw fixtures. It would be nice to have 750mm to be able to crush nose cones, but that's not critical.

Does anyone know how to size and buy a UTM for hobby purposes? I'd even consider building one, but the ones I've seen don't seem like they'd be able to break plywood and G10.

 

[Steve Shannon]

I have some tests I want to do on rocket construction, specifically comparing 3D printed parts to traditional techniques, for which I need a UTM.

However, I don't know enough about them yet. First question is what capacity do I need? I want to be able to do basic tests such as tension and 3-point bend on materials such as plywood and G10. I also want to be able to do compression tests with a piston on assemblies such as a MMT inside a body tube and pull tests such as ripping fins off.

Second question is how can I get one for a not-crazy price? I got a quote for a 30KN machine from Instron and as you might expect, that's too expensive. I don't care about formal calibration (as long as the numbers are close to accurate and consistent). I looked on AliExpress and they have machines for about a tenth of the price, but I'm guessing they're not complete (load cells, fixtures, computer, software, etc.).

Volume is probably where I'm most flexible. I think 500mm should be enough for compress and pull tests where I don't need to use the jaw fixtures. It would be nice to have 750mm to be able to crush nose cones, but that's not critical.

Does anyone know how to size and buy a UTM for hobby purposes? I'd even consider building one, but the ones I've seen don't seem like they'd be able to break plywood and G10.

This sure makes me miss Drake.

 

[fyrwrxz]

This sure makes me miss Drake.

You are one of the few who would even know. That was a blast from the past!

 

[Steve Shannon]

I have some tests I want to do on rocket construction, specifically comparing 3D printed parts to traditional techniques, for which I need a UTM.

However, I don't know enough about them yet. First question is what capacity do I need? I want to be able to do basic tests such as tension and 3-point bend on materials such as plywood and G10. I also want to be able to do compression tests with a piston on assemblies such as a MMT inside a body tube and pull tests such as ripping fins off.

Second question is how can I get one for a not-crazy price? I got a quote for a 30KN machine from Instron and as you might expect, that's too expensive. I don't care about formal calibration (as long as the numbers are close to accurate and consistent). I looked on AliExpress and they have machines for about a tenth of the price, but I'm guessing they're not complete (load cells, fixtures, computer, software, etc.).

Volume is probably where I'm most flexible. I think 500mm should be enough for compress and pull tests where I don't need to use the jaw fixtures. It would be nice to have 750mm to be able to crush nose cones, but that's not critical.

Does anyone know how to size and buy a UTM for hobby purposes? I'd even consider building one, but the ones I've seen don't seem like they'd be able to break plywood and G10.

Although I spent time on an Instron back in Materials lab, I’ve never had occasion to spec one out. They’re big, expensive, and require upkeep. Could you possibly approach a local engineering college? Maybe some students would even be available to help.

 

[Steve Shannon]

You are one of the few who would even know. That was a blast from the past!

In God we trust; all others bring data!

 

[jderimig]

What's your budget? Mark-10 machines are what we use at work for a variety testing similar to this.

https://www.ebay.com/itm/1157737015...d0PODJk5bpF4ttxSEzSQBtVg==|tkp:Bk9SR87zvu38YQ

 

[jsdemar]

https://www.interactiveinstruments.com/materialtesters/
$33k. There might be older models or used models available. They used to make student-level models. I have one of their wind tunnels.

I worked with one of the guys who founded the company. 30 years ago.

 

[prfesser]

As an inveterate DIY-fool, a manually-operated compression/tension machine might not be too hard to build. Commercial machines are designed for production and turnkey operation, hence their cost. A device for occasional testing could be fairly simple.

An ordinary hydraulic press frame might be rigged to work. Add a load cell and associated electronics.

Two challenges I can see of the homemade approach would be (A) calibration and (B) fixtures to hold the items under test. Calibration under tension could be performed with a pressure gauge screwed into the jack. That measures oil pressure but the force can be determined from the jack piston diameter. Fixtures would need to be designed to ensure that failure occurs in the joint under test and not in some other part.

 

[Josh Anderson]

You should check out CNC Kitchen on Youtube. I know he made his own UTM for testing 3D printed parts, and it looks like its even open source too. I'm not sure if it is big enough, but it might be some good inspiration if you havent seen it yet.

 

[JohnCoker]

Could you possibly approach a local engineering college? Maybe some students would even be available to help.

Yeah, I'm pursuing that angle too. Tom Rouse has some contacts at SJSU and is finding out what equipment they have.

 

[kramer714]

John,

I agree with the 'contact a college' comment, having said that MANY of these test can be done with simple mechanical machines. One of the biggest issues is how you attach to the machine in compression without inducing bending moments. Apples to Apples testing for material allowable calculation (A-Basis and B-basis) need VERY specific coupon configuration, functional testing of say a fin attachment, needs a more custom configuration. Years ago I was in charge of a test lab at a manufacturing company, plus have done materiel and product qualification testing.

Mechanical testing using a fixed pivot arm and a weight can be used for MANY of these tests using a simple dead weight or water as the load. I did a military drone wing (6 foot wing) qualification testing using pulleys, water as the load and a simple load cell. Turns out measuring the water in 'the bucket' was more accurate than the load cell. Have done the same on 16 foot long wind turbine prototypes.

Contact me off line, I would be interested in what you are doing and may be able to help.

Mike K

 

[kramer714]

Oh one more thing, if you do this kind of testing, it is VERY important to control the manufacturing parameters, or at least record them. It is really simple to control the fabrication inputs, Some examples,

with PET-G the strength of a part is affected by moisture, were the rolls dried before printing?
Has the diameter of the filament been verified?
Is the extruder calibrated?
Has the void content been verified for the parts?
Are you heat treating / annealing? (what method, how controlled?)

Mike K

 

[bjphoenix]

Matthias Wandel has done some testing on his youtube channel. Also project farm builds various rigs for doing tests of specific things.

 

[Sandy H.]

I work in the 'stretching metal' business and also in the testing force business (kinda related) and I *think* you could do the project with an H frame press from Harbor Freight (or similar) by adding a load cell and MCCDAQ module for between $1000-1500-ish. The tooling to hold and make things work would be per project, maybe, but depending on the scope and resolution of the data, it might be cheaper.

When in doubt, go back to first principles (IMO) and if you can do it with a bucket of water and a scale, then do that. If you need hydraulics etc., then go that route, but dumb the problem down as far as possible before buying anything. (again, IMO).

 

[bcchurch]

Following up on Steve Shannon's and kramer714's comments about engineering schools...

If you were local to Milwaukee I'd invite you in to my lab - we have a 250kN Instron for standard tensile, compression, and 3-point bend tests. Can be adapted to more specialized fixtures but as others have noted special fixtures will require a lot of planning and detailed work. Have you thought about a local engineering school that has a rocketry club? Most universities with a mechanical engineering dept have a collection of these frames. And they are also common for Materials Engineering (my area), Civil / structural, and biomedical. I imagine a team of rocketry-minded students could be trained on the use of the Instron, you could mentor them as to what to test and provide samples. Many schools allow student groups free access to resources like this (I do...). The egg-head professor (me) would not mind about using the frame as long as the students were trained well and are responsible (such students do actually exist). Another benefit (for the students and you) is that the students have access to ASTM specs and can help design tests that follow accepted practices. Get the right group and they could incorporate things like this into their various rocketry design competitions? And heaven forbid they might just learn something practical!! Another idea is to find a school with a SAE (society of automotive engineers) team - those teams design and build various race cars / carts and are often VERY hands on in the labs with mechanical testing and there is some overlap with using 3D-printed parts so the students might have interest. The challenge is getting that magic combination of available test frame, free labor, labor that is actually interested and motivated, and having all of that conveniently located to you.

I think the DIY route is a great path as well. Having the things in your own shop would be a huge benefit for anything time sensitive or that requires specialized fixtures. And calibration (in my opinion) is not super critical since you are comparing A-to-B within your own test environment and not comparing your test of sample A to the test of sample A done by another person or using the measured values for safety-critical design information (I'm assuming here...) Places like Omega sell decent load cells and companies like MCCDaq sell reasonable data acquisition devices but even on the cheap that would be $500-1k for a load cell setup. Buckets of water (kramer714's suggestion) would let you put that money to work on something else and I agree it would give you just as good of a test result. jderimig's ebay suggestion is great (IMO) and would probably get you up and running much faster than the DIY approach and quite possibly at a similar total cost.

Your question about how much load capacity you would need: I would guestimate 1,000 to 5,000 lbs but remember that your loads scale with the size of your samples. If you can scale down your sample size, then you can scale down your required loads.

PS: thanks for your website. I've learned a lot from your site and YT videos.

 

[JohnCoker]

Thanks all. Since I don't know what force is needed, I think I'll either work with a college or send the first samples to a testing lab. I do eventually want my own machine, but I don't know the specs yet.

 

[jsdemar]

Thanks all. Since I don't know what force is needed, I think I'll either work with a college or send the first samples to a testing lab. I do eventually want my own machine, but I don't know the specs yet.

Here's Drake Damerau's website on archive.org...
https://web.archive.org/web/20110727222412/http://www.rocketmaterials.org/
You may be able to determine the peak forces required from his results.

The MTS C43 model is popular in colleges. 2K to 10K pound options. Chinese clones are $6K delivered.